LED-based light fixtures are becoming increasingly more common, and manufacturers have designed LED luminaires to replace rectangular fluorescent light source fixtures. In some designs intended for indoor industrial use, the LED luminaire includes an integrated backup battery and emergency lighting circuitry that operates when AC power is removed (for example, during a power failure, or when the AC power to that luminaire is switched OFF). Thus, such LED luminaires may be purchased and installed alongside LED luminaires that do not contain a backup battery and/or emergency lighting circuitry, so that when AC power is removed a portion of the LED light fixtures in the room or warehouse illuminate to provide some lighting coverage (for example, every tenth LED luminaire ceiling fixture in a warehouse may include a backup battery and emergency lighting circuitry so that when AC power is removed at a warehouse, for example at closing time or at the end of the day, it is still possible for security guards to patrol and/or security cameras to provide images). However, the integrated backup batteries have a limited life, and LED light fixtures that contain integrated batteries can be expensive to purchase and install.
Some other conventional emergency lighting systems utilize a global back-up battery that typically is connected to only a small percentage (such as ten percent or less) of the LED light fixtures of the system. Thus, in a warehouse setting, for example, only ten percent of the LED lighting fixtures would illuminate during a power outage, and only for a limited amount of time as such global backup batteries may have a limited life (for example, one to two hours).
The present inventor recognized that a need exists for a battery backup system for LED luminaires that utilizes a global backup battery to provide adequate emergency lighting capability, and that operates efficiently in a lower power mode to provide extended backup battery life.